New flame retardants but same environmental worries

Blog Post

Worries about the toxicity, environmental persistence and bioaccumulation of the flame retardants know as polybrominated diphenyl ethers (PBDEs) led to their withdrawal from the global market and their addition to the Stockholm Convention on Persistent Organic Pollutants. They have been replaced by new brominated flame retardants (BFRs) like 2-(ethylhexyl) 2,3,4,5-tetrabromobenzoate and decabromodiphenylethane.

In addition, organophosphate esters, a long-established flame retardant group of chemicals used as flame retardants, have grown in popularity since the PBDE ban. These are mainly chlorinated species like tris(2-chloroethyl) phosphate (TCEP) but some halogen-free compounds like tricresyl phosphate are also distributed.

Finding substitutes for harmful chemicals which enter and persist in the environment was essential at the time but the replacements might not be the godsend that they were meant to be. Some of them, notably TCEP and tris(1,3-dichloropropyl) phosphate, are suspected carcinogens and mutagens. Others are known to be toxic to aquatic wildlife.

Of course, none of this matters if the chemicals remain in the materials they are intended to protect. But, you’ve guessed it, they don't. Like the PBDEs, the organophosphate esters and the BFRs are not chemically bound to those materials and leach into the environment.

And they undergo long-range atmospheric transport too, according to scientists who have just found evidence of them in the Arctic. Collecting atmospheric particles from Svalbard, which is a group of Norwegian islands in the Arctic Ocean, researchers from the US and Svalbard analysed them by mass spectrometry as they reported in Environmental Science and Technology.

The mean concentration of all the organophosphate esters combined was 430 pg/m3, compared with a global atmospheric background level of 200-400 pg/m3. The most abundant species were tributyl phosphate and 2-ethylhexyl diphenyl phosphate. The esters that did not contain chlorine were the largest fraction, showing that they also survive long-range transport through the air.

The mean levels of the BFRs in the Arctic air were 15 pg/m3, with total PBDE concentrations making up about 37% of this total. This tells us two things: the PBDEs are still present in remote places around the globe but the BFR levels are overtaking them.

Bearing in mind that we know relatively little about the environmental transport of the many of these chemicals, these results will help to build up a picture of the distribution of the replacement flame retardants and assess the risks to wildlife and, ultimately, humans.